使用sass混合指令

$breakpoints: ('sm':'only screen and (max-device-width: 1024px)','md': 'only screen and (min-device-width: 1025px) and (max-device-width: 1680px)', 'lg': 'only screen and (min-device-width: 1681px)');
@mixin respond-to($screensize){
 $value: map-get($breakpoints,$screensize);
    @if not $value{
     @error 'no value found'
    }
    @media #{$value}{
     @content;
    }
}

@mixin respond-font-size($sizes){
	@each $key,$value in $sizes{
     		@include respond-to($key){
        		font-size: #{$value}px;
        }
    }
}